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William Miller William Miller is offline
Registered User
Join Date: Mar 2003
Location: Darnestown, Maryland
Posts: 913
Thanks for the food. I need to digest a while.
I was spinning this arround in my head last night and woke up with an idea.
As I mentioned above, my control pressure regulator effects control pressure from 3 things. Tempature, Manifold vacuum, atmospheric pressure. I forgot 1 device that I think was added on by Porsche because it's not made by Bosch. The Thermo Valve. This valve is in the vacuum line that goes from the Control Pressure regulator to the throttle body. It's normally closed and opens in 10-30 seconds as it's internal heter element warms up.
I think this may be a good control point.

The specifications book (little book) shows that warm control pressure shoulb be 3.4 - 3.8 bar with vacuum (Like at idle and light cruise) and it should drop to 2.7-3.1 without vacuum (Like at full throttle). I would imagine that the change in pressure is in some relation to the change in vacuum. So I don't think this operates as full open or full closed, but modulates gradualy with the change in vacuum. Internally it's done with a diaphram and counteracting springs.
Again this is the full throttle compensation design for my car. Maybe a little more eloquent than the throttle position switch?

So I'm thinking if I can replace the "Thermo - valve" with a valve that is controlled by the LM1 I might have a chance.

I like the idea better than the earlier because:
1. I don't have to screw arround trying to find something rated for fuel and screw arround with the stock plumbing.
2. The stock fail safe functions would remain in place.
3. The vacuum diaphram has a built in upper and lower limit of control.
4. I think / hope this is a large enough range of control to keep the A/F ratio at the right spot for different engine conditions.

Does anyone think this will work?

I think a simple Pressure electric valve would work as an on off. (not exactly what I want.) I'm pretty sure they make modulating valves in the 0-5v operating range. I know they make them for pnumatic building controlls, but that's pressure, not vaccum.

Any help on this is greatly appreciated!
Bill Miller
81 Targa Guards Red
3.6, M&K 1 out, S4 brakes
83 ROW CAB Rubinrot Metallic (RIP)
Old 01-27-2005, 01:06 PM
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